Which one of the following is used in preparing a natural mosquito repellent?

Lemongrass (Cymbopogon citratus) is widely recognized for its natural insect-repelling properties. It contains essential oils, particularly citronella, which is a well-known active ingredient in many natural mosquito repellents. The oil extracted from lemongrass is commonly used in candles, sprays, and lotions to deter mosquitoes and other insects.

A) Congress grass (Parthenium hysterophorus) is an invasive weed known for causing allergies and ecological damage, not for repelling mosquitoes.

B) Elephant grass (Pennisetum purpureum) is a tall perennial grass used primarily as fodder or for biofuel production, not as a mosquito repellent.

D) Nut grass (Cyperus rotundus) is a common agricultural weed and is not known for mosquito-repelling properties.

Therefore, lemongrass is used in preparing a natural mosquito repellent.